This proposal has two main foci: the chemistry of iron porphyrins and the nature of chemical bonding to the proton (H+). The broad objective is to uncover new fundamental chemical knowledge that provides the basis for a molecular level understanding of hemoproteins and protons in chemical and biological systems. Specific objectives in metalloporphyrin research include: (i) the further development of a magnetochemical alternative to the familiar Spectrochemical Series, (ii) testing the applicability of the magnetochemical concept in a series of met-myoglobin derivatives, (iii) revisiting the concept of quantum mechanically admixed S = 3/2,5/2 spin states in iron(Ill) porphyrins, (iv) preparing an osmium porphyrin complex with xenon as a ligand, and (v) isolating "sitting-atop" metalloporphyrin complexes -- reaction intermediates in the insertion of metal ions into free-base porphyrins. In research on the proton, intermediates in proton transfer and acid catalyzed reaction chemistry will be investigated. Specific objectives include (i) measuring the acid strength of carborane-based acids, (ii) investigating a new class of short, strong, low-barrier (SSLB) H-bonds (iii) isolating carbocations as carborane salts, (iv) investigating the fundamental chemistry of the hydronium ion (H30+) in water-deficient environments as models for enzyme active sites and membrane channels and (v) developing the chemistry of a new, strong, methylating reagent. Emphasis in these studies is placed on the definitive characterization of analytically pure materials by X-ray crystallography, a variety of spectroscopic methods (NMR, IR, electronic spectroscopy including NIR, Mossbauer, resonance Raman, etc.) and theory. Fundamental chemistry is the hidden engine of biomedical science. There are potential applications of carborane acids in steroidal metabolism disorders and MALDI protein analysis.